Get some Toyota brand fuel injector cleaner from your local Toyota dealer or
Chevron Techron from your local parts store and follow the directions on the
bottle.  Basically, you add it to a half tank of gas and use it up within a
week.

My mechanic recommends a gasoline additive called Techron, added once or
twice a year. He doesn't sell it, so I figure he's being honest with this
opinion. Auto supply places carry it. I haven't noticed a difference after
using it, but I also did not notice a problem BEFORE using it. Draw whatever
conclusion are convenient, based on my shoddy research.

YUP - Chevron Techron available at Target and Advance Auto. Add it to tank
of gas. Works great on my Yotas.